I don't think it is gonna get anymore updates. They have moved on to the next game and have already done a dlc to Hydroneer. I think it is what it is.

The way I used to do it a long time ago is to pick up a bucket and drop it at slowly increasing distances .
Each time you drop it in range of the sprinkler it will fill with water.
Pick it up and empty it , repeat.
I don't believe it will fill up if you just hold it and walk around.
It's a little more work but once you get the idea you won't have to keep doing it.
Tip: water will go through materials,(wood platforms,the ground, if you put something underground to grow.)
The game is complete so I doubt they will make it easier.
Have fun..